Remote-control system



Sept. 19, 1950 E. s. PURINGTON REMOTE-CONTROL SYSTEM 5 Sheets-Sheet 1Filed April 5, 1945 INVENTOR. E; L 504 J. Pun/V 70 A T TORNEV Sept. 19,1950 E. s. PURINGTON 2,522,893

REMOTE-CONTROL SYSTEM Filed April 5, 1945 5 Sheets-Sheet 3 INVENTOR. 5401v J. IOUE/NG ro/v ATTORNEY Sept. 19, 1950 E. s. PURINGTONREMOTE-CONTROL SYSTEM 5 Sheets-Sheet 5 Filed April 5, 1945 W MTM u whNM. u mw IN V EN TOR.

. Nah QYX flL/JQN 6T UR/NG TON BY #44 A TTOR/VEV Patented Sept. 19, 1950REMOTE-CONTROL SYSTEM Ellison S. Purington, Gloucester, Mass., assignor,by mesne assignments, to Radio Corporation of America, New York, N. Y.,a corporation of Delaware Application April 5, 1945, Serial No. 586,781

Claims.

This invention relates to an improved method of remote control by radio,permitting the independent execution of two control operations. Forexample, as applied to the control of an airborne craft, it provides forleft or right rudder, and also for up and down control of elevation,either independently or in combination.

One feature of the invention is that the system cannot be readilyoperated by the types of transmitters commonly available. Hence aconsiderable degree of security is provided.

Another feature is provision for the introduction of irrelevant signalsso that unauthorized parties will be confused in making analysis of thesystem which is being employed.

In the operation of the invention a continuous carrier wave is radiated.This wave is then'modulated by selected ones of four different signalfrequencies applied in periodic succession, with substantially a quarterof the operating time devoted to each signaling channel. During selectedcyclic periods of allotment of the signals to the multiplex channelsalternating currents are built up in corresponding receiver channels,with phase separations by 90 electrical degrees, or multiples thereof.The control operations are determined by the phase relations of thecurrents by the use of phase comparator circuits.

Fig. 1 shows a form of transmitter;

Fig. 2 shows the first portion of a radio receiver cooperating with thetransmitter of Fig. 1;

Fig. 3 shows a tuned type phase comparator system for use with thereceiver of Fig. 2;

Fig. 4 shows an aperiodic type phase comparator which can be used withthe receiver of Fig. 2, alternative to that of Fig. 3.

Fig. 5 illustrates a generalized method of operation in accordance withmy invention.

In Fig. 1, a master carrier wave source I [I is operatively coupledthrough a capacitor II to a modulated power amplifier 20, which deliversamplified power output to antenna 30, modulated in accordance with thesignal pattern impressed upon the control grid of modulator 40. Theinput circuit for tube 20 includes a choke l2 andv a resistor I4connecting the control grid to ground. Resistor i4 is shunted by acapacitor lit. The output circuit is fed with direct current anodepotential from the source l1, connection being made from the anodethrough a. chok I9 and the primary winding 2| of an output transformer.The inductance 2! is parallel-tuned by a capacitor 22. One end of theparallel-tuned circuit 2l-22 is connected to ground throug'hja capacitorl8 which is chosen as a low impedance to radio frequency currents and asa virtually infinite impedance to audio frequency currents. Thetransformer primary 2| is coupled to a secondary which feeds energy tothe antenna 30. A cathode resistor l5 connects the cathode andsuppressor grid to ground. This resistor is shunted by' a capacitor I6.Screen grid potentia1 is supplied from the source I! through a resistor23. The screen grid is connected to the cathode through -a capacitor 24.

Through the choke l9 anode potential is als fed to the anode of theamplifier tube 40. This tube is shown as a triode but other types oftubes may be used, of course, if desired. The cathode is connected toground through a cathode resistor 2t which is shunted by a capacitor 21.The input circuit includes a grid resistor 23 connecting the grid toground. Connection is also made between the control grid and the slipring of the commutator 41 hereinafter to be described in more detail.

Four selectable frequency sources 4|, 42,43, 44 are provided, which maybe operatively connected to the input of a modulator 40 under thecontrol of relay devices 45 and 46, and in accordance with the operationof a commutator 41, driven by motor 49. The relays 45 and 46 in turn arecontrolled by key sets 5| and 52, with the former used for example forright or left rudder, and.

might be 52, 64, 56, and 68 kilocycles respectively,

and the commutator device might be rotated at a frequency of revolutionsper second. The arrangement of the keys and relays shown providesleft-right control of the rudder and at the same binations are possible,namely right, left, up,

down, all individually, or right-up, right-down,

left-up, left-down in combination. When a key is in neutral, there is nooperation corresponding to that key. These controls determine the orderin which the various frequency sources are impressed upon the modulator48 by the commutator device 41, and therefore the order at which peaksof energy occur in corresponding receiver circuits to be describedlater.

In more detail, the key is provided with a moveable contact member 53,and contacts 55, 51. Contact 55 is connected through relay winding 59and. contact 51 is connected through relay winding 6| 'toground, oneside of -battery-63 being grounded. The other side ofithis battery isconnected to the moveable key contact. The windings 59 and 6| are onopposite legs of a balanced relay 45 having an armature 61 which isoperatively connected by insulating member "69 to moveable blades H, 73of a double pole double throw reversing switch, with outer contacts 15,11 joined together and to one terminal of source. 4|, and inner contact19 connected to one terminal of source 43. The other terminals ofsources 4| and 43 are grounded. Spring pressure is exerted opposinglagainst the-insulator 69 by contacts 1| and:='|3, thus normal-1ycentering the relay armatur5l and breaking all contacts when neitherofthe windings 59 or 6| are actuated. The contacts H and 13 are connectedrespectively to segments 85 and 81. "mut'ator 41 has a slipring 89 whichiss-wept by The coma brush 93 mounted on a rotary brush arm 9| "drivenby a motor 49. The brush, therefore, con- "nects each of the commutatorsegments in suceession to the slip ring. The segments are insulated fromeach other, and occupy the four "quadrants of the commutator periphery.

The key 52 for up and down operation, its associated relay 4B andcommutator connections are similar to those for key 5| and need not bedescribed in detail, other than to catalog the items.

When the key 52 is moved to the up position con- "tact54' is engagedwhich energizes the winding 62 on relay 46. 'When the key is moved tothe down position contact 56 is engaged which energizes winding 60 onthis relay. The contact spring arrangement operated b relay 46 includesmovable contacts 12 and 14, outer contacts 16 and '18, and themiddlecontact 80.

generators 42 "and 44 are connected to the outer and inner cont-actssimilarly to the connections The tone described for generators 4| and 43and their associated relay contacts. The movable contact f is connectedto segment 84 on the commutator 41; while contact 14 is connected withcommutator segment 86.

'As previously stated, the slip ring '89 is con- -nected to the inputgrid of modulator-4D, which is connected to ground through resistor 28.I a result, thesegments 81, B5, B6 and 84 are connected to the modulator40 in rotary succession, "so that its input is energized in successionfrom whatever voltages are impressed teadily upon these four segments.

With the choice of right-down control, as indicated, the sequence ofthis four frequency pat- 'tern' will be f1, f3, f2, f4, which sequenceis repeated during each revolution of the brush arm 9| at a speed, say,of 100 revolutions per second.

' It will be clear from the above description that The signifiupon theapplication of the tone frequencies as modulations in differentsequences. If only one of the keys, say key 5|, is actuated then a rightindication will be represented by the immediate sequence of frequenciesf1 and f3 in that order, while if this key is moved for left indicationthe frequencies will be is and ii in that order. The key 52 beingunactuated no modulation frequencies will be sent out While the brush 93traverses segments 86 and 84. Other sequences of the tone frequencymodulations or frequencies f1, f3, f2 and it may, of course, betransmitted, depending upon the remote control operations: to beperformed.

The modulating frequencies are recreated at the receiver by use of anarrangement such as --shown in Fig. 2.

Signals from transmitter antenna 30 of Fig. 1

are received by antenna I00 of Fig. 2, tuned to 0 carrier w-a-veresonance by radio receiver lfll,

and impressed, either directly or after conversion to an intermediatefrequency, upon the control grid of detector H12, preferably of thesquare law, plate detector type. The output is selectively transmittedthrough frequency discriminator I05 to energize amplifier I I3 mostcompletely from detected energy or frequencies" corresponding to"transmitter sources 4 "and 43) for right-left con- "trol, and amplifierl'l lmo'st completelyfrom detected energy or frequenciescorresponding totransmitter sources '42 and' 44" for up-downcon- 'trol. Afteramplification in H3, a further-discriminatorl 'actuatesdetectors [33 andI35 most strongly for the" frequencies corresponding 'to sources 4| and43. Similarly detectors I34, I36 are most strongly actuatedfrom"so'urces"42 and 44, the received'signal"energy"being "fed throughthe discriminator Ha. I

These detectors are provided with output'circuits with designs-such as'tosmooth out the detected outputs to produce 'voltages at'terminalsI63; |65,I64, 1660f the frequency corresponding to the rotation ofcommutator 41, but the relative phases" Of the currents will bedetermined by the signal sequence. For the transmittercase given,

the voltage peak at terr'ninal*|63 will lead th'evoltage'peak atterminal |65-by90 electrical degrees, at 'l00'cycles per second; whilethe voltage peak at terminal-1B4 will lag*behind the voltage peak-atterminal |6B*by 90 electrical degrees.

It will be understood by those'skilledin theart "that the choice offrequencies for actuation of the selective circuitsis arbitrary, andneed "not conform to What-=is -herein 'illustratively stated.Furthermore the circuits themselves may be modified in design, as forexample, by-use of more selective circuits, for thefrequenciescorresponding-to transmittersources 4| to '44 and for theoutput frequencies corresponding to the rotary speed of themotor'49.

In addition to the receiver equipment'of'FigpZ, phase comparators are:required forthe' outp'uts of Fig. 2. Although such devices havebeenshown elsewhere, they A are not-= generally known and two arrangementsareliereshown. Fig. 3 shows a transformer type with inputs numbered'toopcondenser [65a to the grid of amplifier triode I10,

which in turn is connected through resistor I65b to ground terminal I61.The impedances of elements I63a, I63b, I65a, I65b are all chosen to besubstantially equal at the recurrence frequency, say 100 cycles,.so thatthe voltage on the grid of triode I leads that on terminal I65, whilethat on the grid of triode I69 lags behind that on terminal I63 both by45 electrical degrees.

The cathodes of triodes I69 and I10 are connected together and to thepositive end of battery Hi, the negative end of which is connected toground terminal I61. The plate of tube I69 is connected through resonahtcircuit I13, I14 and the plate of I10 is connected through resonantcircuit I15, I16 to the positive end of battery I12, the negative end ofwhich is connected to the cathodes of tubes I69 and I10. The resonantcircuits are tuned to the frequency of recurrenc such as 100 cycles inthe illustrative case. If a convention is adopted that currents arepositive in the direction shown, then the currents in coils I13 and Iwill be in phase provided the grids of tubes I69 and I10 are excited inphase, that is if the voltage at terminal I63 with respect to groundleads the voltage at terminal I 65 with respect to ground by 90electrical degrees. But if the voltage at terminal I63 lags behind thatat terminal I65 by 90 degrees, then the grids of tubes I69 and I10 willdiffer in phase by 180 degrees, so that currents in resonant inductors I13, I15 will be oppositely phased. But if voltages on terminals I 63 andI65 are like phased or in phase opposition then the currents ininductors I13, I15 will be difierent in phase by 90 degrees in apositive or in a negative sense.

For the case illustrated, since the transmitter source 4| is connectedto the modulator just prior to source 43, and since detectors I33 andI35 are responsive to currents of th frequencies of sources 4| and 43,it follows that the voltage on terminal I63 is leading that on terminalI by 90 degrees, thereby causing the currents in the inductors I13 andI15 to be like phased.

The inductors I 13 and I15 are coupled to a pair of independentlyoperating rectifiers I8I, I82, by means of four secondary windings I11to I 80 inclusive. Preferably the inductors are equal, the couplings areequal and the mutual inductance between each secondary and its primaryis the sam as for any other secondary and its primary. One of thewindings, such as I11 is reversely coupled, that is in an opposite senseto the others.

One end of coil I11 is connected to the anode of rectifier I8I the otherend of I11 is connected through coil I10 to ground. The cathode ofrectifier I8I is connected through resistor I83 to ground. The voltageimpressed into this rectifier circuit is proportional to the vector sumof the currents in the coils I13 and I15. On the other hand, one end ofcoil I19 is connected to the anode of rectifier I82, the other end ofcoil I19 is connected through coil I 80 and resistor I85 to the groundedcathode of rectifier I82. Here the couplings are such that rectifier I82is driven in accordance with the vector difference of the currents inthe coils I13 and I15. Condensers I84 and I86 are bridged acrossrectifier output resistors I83 and I85 for reduction of A. C. componentsin the output. For the case given, with voltage at the terminal I63leading the voltage at terminal I65 by 90 electrical degrees, therectified current through resistor I83 will-be greatly in excess of therectified lcui rer'itl through resistor I85. On the other hand if the--oppositephaserelation held at the input terminals, the current throughresistor "I85 wouldgreatly exceed that through resistor I 83. If,

however, the voltages at terminals 163 and I 65 are like phasedoroppositely phased, then the two currents in resistors I83 and I 85-wouldbe equal. 1

The cathode of tube I8I is connected through resistor I81, to the gridof a triode I90, for con-.- trolling a relay 92. The junction of coil- Iand resistor I likewise is connected through resistor I88 to the grid oftriode I90. Resistors I 83 and I85 are preferably equal, and resistorsI81 and I88 are preferably equal but-of much" greater resistance thanresistors I63 and I85.. Condenser I09 may be connected from the gridsoftube I90 to the ground line. The anode oiv, tube I 90 is connectedthrough one winding93- of relay 92 to the positive terminal of a batteryI9I, the negative terminal of which is grounded. The cathode of tube I90is connected through 1 resistor I to the positive terminal of battery,I9l, also through resistor I93 paralleled by condenser I94 to ground.Relay 92 is provided with an armature 90 having control over a lever,which. terminates in an insulatingbutton 69 for jointly; actuating twomovable contact blades 91 and'98., Between these two contact blades is astationary contact 96. The spring tensions of the contact; blades aremutually opposed so as to normally hold the armature midway between the.pole; pieces of the relay coils 93 and 94. The armature position is,however, a function of the D. C. current in winding 93, this currentbeingnor v mally balanced by current through an opposing relay coil 94.A rheostat 95 is in circuit with coil 94 and by adjustment thereof theenergiza tion of coils 9 3 and 94 can be brought into mutual balanceunder the no-signal condition. Thecontact 96 is connected through abattery I99 to terminals of two D. C. motors 200 and-20l, the otherterminals of which are connected to .the contacts 91 and 98. I

The constants of the relay circuit are so. chosen that when the grid ofI90 is at ground 5 potential, current flo'w through relay coil .,9 3.,will hold both contacts 91 and 98 open; will occur when the outputs ofthe rectifiers 'I8 I',=--i I82 are balanced so that the junction pointof resistors I81 and I88 is at ground potential; When, howeventhecurrent through resistor I83;- exceeds that through resistor I85 due tothevolte 1 age of terminal I63 leading the voltage of ter-' minal I65,then the potential of the grid of tube I90 increases, and increasedcurrent in coil 93...

causes contacts 96 and 98 to close, thus driving, motor 200. This causesright operation ofthei; rudder in accordance with operation of key 5L.(Fig. 1)- to right position R. If, however, the key, 5| were at positionL, then the voltage at ter,-,

minal I63. would lag behind that'at terminal I6,5,,.;

the current through resistor I85 would exceed, that through resistorI83, and the grid of tube I90 would be negative with respect, to ground.

Under these circumstances, the current through relay coil 93 would bereduced, the armature 90,. being then attracted predominantly bycoil94,. thus producing a circuit closure throughcontact 91 which operatesmotor 20I for left rudder control. 1 Freedom from operation byunauthorized types: of transmission will depend uponthe lackof defite.pha e re a io s p at he. input terminalsa '7v ltiamhi .65 'of- Fig-:3.Onlyl; whensthe signals; are: suitablysphaseerehted: will the.rectifiedl outputs; of diodesll 8.l.and.:| 82 differ suflicientlyrtoproduce, anaeffective changelinthe impedanceiof tube I901. andaresultant. actuation of relay 92.

In Fig: 4 arr-alternative type:oicomparatonds. shown;v with conditionscorresponding .to thezvolt l age o;fi terminal ;;|64 lagging.90electricalv degrees-: with respect to that at terminal I66, as whenthis; circuitjs connected to correspondingpnumbered terminals of. Fig;.3. This comparator does notrequirertuned circuits, and would beespecially. useiuluwhen the recurrent rate is quite. low; Inthisx-figure both retarding and advancingmircuits areeemployed. betweeneach input: termination ands-the common ground. These circuits 'arecross-connected to two twin-triodes 2l0 and 2| One;-discharge.path ineach of these. tubes? is-arrangedto bev actuated' more strongly thanthe. other..

Theaphase retarding and advancing circuits: compriseeleinents 202 to 209inclusive, all of which-"are of thesame impedance at theoperatingirequency. Retarding circuit comprising resistor' 202'in serieswith condenser 203andadvancingcircuit comprising condenser 206 andresistor 201 are connected in parallel between terminals|64 and I68.Similarly retarding circuit comprising resistor 204 in serieswith-condenser- 205, and advancing circuit comprising condenser- 208 'inseries with resistor 209 are connectedin parallel between terminals I66and I68. The junctionsof elements 202 and 203, and of elements 208'and209- are connected to the two con-'- trol grids of twin-triode amplifiertube 2l0, and the-junctions of elements 206 and 201, and of elements204- and 205 are connected to the two controlgrids of twin-triodeamplifier tube 2| I. The cathodes of these twin triodes are connectedtogether and to the-positive end of battery 2|2, the negative-end ofwhich is connected to grounded terminal I68. The negative end ofbattery-H3 is connected to the cathodes, while the positive endofbattery 2|3 is connected through resistor- 2 M to the two plates of tube2l0 and through resistor 2|5 -to the two plates of tube 2| I. These twotwin-triodes 2 I and 2| I serve as mixing amplifiers; developing anoutput plate voltage in accordance with'the vector sum of the voltageimpressed -upon the two grids.

For the arrangement given, with the voltage at-ter-minal I66 advancedwith respect to that at terminal-164, the-two grids of 2|0 areenergizedoutof phase, but-the two grids of 2| are energized in phase Therefore alarge output voltage develops at the plates of 2| and little or novoltage at the-plates of tube 2l0. If on the other hand,

8.... throngnrr'esistonsn l will .be; muchsgreater. than;that-throughresistor 2|9.. The cathode. ofi rectifier 21.1. .isconnected :to .ith'em gridmf relay-tubez226 and. that. of rectifier.222.

is.connected..to the grid of relay tube22l. The?! thevoltage-at terminalI64 should lead that at I terminal |66--by 90 degrees, the tube2|0-would develop largevoltageand tube 2|| a small voltag.e.= For equalphased or reversed phased inputs; the tubes would produce equal-outputsAlthough-desirable; it is not necessary that theinput voltagesbe ofthesame magnitude.

The plates of tube-2l0 are connected-through condenser -2| 6 to theanode of rectifier 2 |'|,-which inturm is connected through resistor2|8' to 1 ground; The cathode of rectifier 2|1 is 'connected throughresistor 2l0 to ground, and this is: shunted by condenser 220.

Similarly a rectifier outputcircuit is providedfor plate output of tube2 involving elements 221 -170 225 inclusive. For theconditions shown,with the terminal I66 advanced in phase 'with' .ods.

cathodessof .these rtubescarerconnected together. and through resistor.228: to ground, paralleledbyn condenseri.223.. The:plate .oftriode226is. con.-.-. nected-throughwinding 230and the plateof'wtri ode '221.through winding. 23 of a balanced relayt 232@,to.the.positive endofbattery 233,.the negative end of :whichsiseconnected to aground... Resistorz-234fiis connected .between the positive: end: of battery .233and the :cathodes of. tubes 226 and rv 154221:- The balanced. relay 232is providedswitho an armature. 235i and with :armature-controlledtcontacts 236 and 231. 'It responds to an:'un-'-:'- balancemfothecurrents/through itstwo windings.- Contact 236 is connected throughmotor 238and contact. 231 is connected through motor 233: to'

thenegative end 'of battery 240, thepositive end of which is connectedtoa-stationary contact 2M which intervenes between the movable contacts236'and 231.

In operation the" circuits have been adjusted so that in the absenceofsignals, the tubes 226 and 221' pass little-or no current. When inaccordance with operation of key 52 of Fig. l,the transmitter ismodulated by source 44 (frequency f4) and immediately thereafter bysource 42"(fre quency f2) the receiver produces an A. C. voltage atterminal |66-which leads that at terminal l'64 by electrical degrees.This causes a'large D. currentrto fiow through resistor 224 "and a verysmall D. C. current to flow through resistor 2|9,- the latter currentbeing zero when the magnitudes of the two A. C, voltagesare equal. Tube22l with itsgrid more positive thanthat of tube 226, causes-the armature235 of relay 232 to be drawn to the pole-piece on which winding 23-|"islocated,-'- closing the contact 236 andrend'ering motor 238 operative'toexecute the control called for by key-52. If this key werein-neutral,"then= the two currents would be equal and small; so' thatthe armature '235' of relay 232 would be in' neutral: For thekey52on'position-U,the=reverse phase relation would exist at theinputs'of Fig. 4, and the motor 239 would be actuated. In the event ofinterference which actuat'es recti'-= fiers 2H and 222 m an equalmanner, there'will be no output. By choosing the tubes 226*and 22'!withsquare law characteristics, and provid-- ing a relay withlittle-backlash, the operation'o'f the system will be made independent'of the amount of interference of randomhature to-a large degree.

It is evident that while the inventionhasbeen" described on the-basis ofamplitudemodulating'- a radio carrier, it can be practiced by othermeth- For example, a radio carrier can be fre quency modulated toproduce'a plurality of carrier frequency valuesin succession, and thecurrents" necessary for operating the circuits of Fig.2 may;

be produced by heterodyning the radiated fre'.- quency modulatedsignals. The frequencies of the series 11- f4 herein'referredto may,there'-" fore, be considered variations of carrier frequencyassignments, or astone generator frequenciesyac cording to the design ofthe apparatus.

In Fig. 5 the use'of frequencies f1, f2, fa, f4 andis is indicated, ofwhich frequency is may becom sidered serviceable only for camouflagepurposes. A connection panel 50|' comprises a plurality ofi jacks 502each connected to one of the frequency respect to terminallill,the-"rectified cmrent usources -or tone generatorst Another series-ofjacks 503 is suitably connected to contacts of two keys 504 and 505. Key504 is illustratively shown as having the function of right and. leftsteering. Key 505 has the function of up and down steering. Forconvenience the jacks of the 503 series are labeled a, b, c, d and e. Bythe use of jumper wires 506 the jacks 502 and 503 may be interconnectedin any desired combination. The combinations may be changed from time totime according to a secret schedule. In this manner it will be difiicultfor an unauthorized recipient of the signals to analyze the system so asto determine what each signal means. Changes may be made from day to dayor at predetermined times during the course of a run so that thedifficulty of analysis would be greatly increased.

Key 504 has contacts f to o inclusive and key 505 has contacts to 11inclusive, arranged in alphabetical order. The interconnections betweenthe key contacts and the jacks a to e inclusive are as follows:

Jack a is connected to movable contact 2'; jack b is connected tomovable contact 7c; jack 0 has branched connections to contacts n and y;jack (1 is connected to movable contact if, and jack e is connected tomovable contact 1;. Contacts g, o and q are interconnected; contacts hand l are interconnected and are also connected to segment I on a rotarydistributor switch 41' similar to distributor 41 in Fig. 1. Contact 1'is connected to segment 2 on distributor 41'; contacts m and p areinterconnected; contacts 1' and a: are interconnected; contacts s and ware interconnected and are also connected to segment 3 on distributor41'; contact u is connected to segment 4 on distributor 41'.

With the key contact connections arranged as shown it is possible totransmit signals for left or right rudder control and for up or downelevator control and these signals may be transmitted singly ortogether. Whenever they are transmitted singly the camouflage frequencyis is transmitted on one segment of the unused half of the distributor41'. The following table shows the correlation between key contactclosures, and the connections from the jacks a, b, c, d, e to thecommutator segments I, 2, 3 and 4:

Jack Con- Olosure of contact pairs nections to Segments Operation Key504 Key 505 1 2 3 4 Right only" fg, hi, jk, mn qr, w: a b c Left onlygh, ij, kl, no qr, wz b a c Up only gh, mn Pq, st, 1w, wx c d 2 Downonly gh, mn qr, tu. 0w, 11 c e d Right-up... fa, hi, ik. 'nm pg, st, uv,wz a b d e Left-u gh, 1' kl, no P9, st, uv, wa: b a d e Right-down. f0,hi, jk, mu gr, iu, mo, 11/ a b e If Leit-down gh, z'j, kl, no gr, tu,11w. my I; a e d In connection with the above table, it should bepointed out at this juncture that the keys 504 and 505 are of the typeknown and used extensively in telephone practice as anti-capacityswitches, being of the four-pole double-throw type. Such switches areactuated by a cam roller, and standard keys or switches of this typehave the springs carrying contacts i and 7c, and t and 12, under tensionsuch as to hold the corresponding key in a central position. Under theseconditions, whenever key 504 is moved to execute Right operation (handleof key 504 moved to the right) contact i is moved to the left by thecontact with Z, and. at the same time, because of its tension, thespring carrying contact i moves to the right to establish contact with7'. The center contact a of course need not move much from the positionshown in Fig. 5. A similar explanation is applicable to key 505, so-thatthe accuracy of the preceding table should now be apparent;

Fig. 5 also shows modifications of receiving arrangements where thecomparators 3 I and 32 are fed with filtered output components from theunits I33, I35, I34 and I36 with intervening jack panel and jumper wireconnections for adapting the signal responses to the permutationalarrangement of frequencies which at any time may be set up on the jackpanel at the transmitter for assignment to the contacts of keys 504 and505. The receiver circuit components between the antenna I00 and theterminals I63, I65, I64 and I66 may be the same as shown in Fig. 2, andfor this reason such circuit components are not repeatedly shown in Fig.5. They are indicated in their entirety by the rectangle labeled Circuitarrangement of Fig. 2-. The comparators 3| and 32 correspondrespectively with either of the circuit arrangements shown in Figs. 3and 4. The output circuits for these comparators supply suitablecurrents for driving the'rudder motors 200,

20a, 238 and 239, the same as is shown in either of the modifications ofFig. 3 and Fig. 4.

So far as the modification of the receiving equipment is concerned theonly change indicated in Fig. 5 is that of introducing alternativeconnections between the filter circuits I33, I35, I34 and I36 and theinput circuits 33, 35, 34 and 33 of the two comparators 3| and 32.Jumper wires 31 may, therefore, be used for interconnecting the jacks insuitable combinations, thus facilitating the changing of thepermutations for the different controls in accordance with a prearrangedschedule. The right, left, up anddown steering controls may, therefore,be made to conform to the intended remote control significance of thesignals as transmitted, changes being made from time to time in thepermutational arrangement of the tone generator frequencies in order toconfuse an unauthorized recipient of the signals.

The frequency allotments to the transmitting distributor segments aresubject to a certain number of permutational variations. Thus, forexample, assuming that only four frequency selective filters are to beprovided at the receiving station, and that the camouflage; frequency iswill not be interchanged with any other frequency, then in place of theconnection of source h to jack a, either of the sourcesfz, f4 or is maybe connected. With each of these substitutions the remaining frequencysources may be allotted to the other jacks in different sequences,making 24 possible permutations. Since a receiving commutator has beenfound unnecessary, however, the starting point for any sequence ofsignal elements is not distinguishable. Therefore, only six of the 24possible permutations are really useful as follows: a v r 1 4; Thecombinationa'c'condin'g to claim I 2 and source "including meansassociate'dwith the transmitting vliermu'tation apparatus and withithereceiving apparatus f or f f f f transposing Ithe DOSltlOlflS of .thevsignal elements of each'pair in the sequenc'e of transmission. a b d e5. In a radio controlled: system foristeering a g 2 f 5 dirigible body,the 'co'mbination-withlmotor means b a d a Jacksio'r Csettingtherrudd'er'to eitherlside of aneutral g g a position, of aI'FthFEB-IJQSitiOIIF relay i havingr two 8 10 en'ergizing c'oi1s andcontacts for reversiblyz actutin s i UtOIJIIIBBIlSg; lec'tro.itubeztcir'cuit :z-If' desiredpan additional frequency-selective g i gsillectingf and dgtectmgisignalfipulses 2 g gg ggzg f gg 1 ii z ii fgggf gg of different i requ'encya.:charatcteristics:irecuriing at a fixedrate-and aeknowirrsequence 'which may be usefi as subsmtute for any ofthe oufler 15 be'change'abl'e to derive? characteristic potentials, iquencles for control purposes t?- the dlsplaced andmeanszcontrolle'd'lbyizsaid potentialslfor; diffrequency can be igg ig yzg' ferentiallynactu'ating the; coils: of -saidirelay in gggi ggg i g gg si iz s zg gg 2 2 accordance-witlt'theparticular sequence ofrecep- 3"tion-f of saidipulses. 2r transmits; are W hzn :i x/ision i s ma e forinterchanging five and radlatmg Garner frequency energy g g tlatorcircuit tor?whichulsaidwmeans;:is-. cou" e or morefrequencies certain ofthe possible com- :means' forgenerlatingnmodulation 'frequencyienstrainerare:castigated: 250011111111 a ing means :couplingv'saidn asaname n thls manner the m fiecodnilg thegenerating'imeanswtorsaid,modulatorzrcircuit for nals-byan unauthorizedrecipient will be still applying pulseslof ,energywofpdifierent. frequemfi F 'cies from said-modulation frequencygenerating Q modlficatlonsVHF/611151011 y means to said modulator icir'cuit in sequence at be madef a F m the 1n f a substantially fixed pulse rate-said pulses (being orthe foregoingldescription. Such modififia 1011s Jcha-racterized 'byidifierent frequencies 'whichapwillbe understood to be comprehendedwithin the pgar inia predetermined,butachangeable sequence, lscope'of mymv n i'em'otelysituated receiving :andl .demodulating clalm: means,-means forrd-iscriminating'between'difier- A z q f z r'g g 3;sentdemodulation products :of the re'ceived signal 1 y Erna P curren rDe a r t pulses which possess said different frequency productive-0f ifi i g radlgn characteristics,Piphaseshifting devices operable energy erme 11 mg m or at a-frequerrcy-zequal:to rtherlsaid pulserateu-and W wavemeans m'clfldmg fi .-eiTective--to combine said demodulation products,pl dlstnbutor a a keymg devlce 93 l gand-reversiblyoperable.-relay=means--suitably cou- "ifiiiliii ii riiiefiifi liqii fifii t5255a15311"Pied ii g g g gj i sense 0 here ay opera ion is made; epe en 'latmgmeans, said keying device including means upon sequence: of,ltheffmodulaitionfifrequency 'to-vary the sequence of the generatorconnec- Hpulsea *tions, a receiver comprising selective means for The,combination accordingtwclaimGrand discriminating between the respectivefrequencies including mutually opposed? motor r .rfor the slgnalsomgma'ted at Sam transmltter and steering a dirigible rbody,and-circuitscontrolled detecting means P diffierens by said relay meansfor selectively actuating said uquencies; coupled to said discriminatingmeans motor means thereby to steer said body in a producing Voltagescorresponding time tion which is determined by the joint control sig--quence to the sequence of modulation of said 1 mficance of saidmulseS"Wave by the alternating currents 8. The combination according toclaim-61=and Phasedisplacingmean? combination with including afour-channel distributor in said comlecting means for 'comblmng saldVoltages to mutating means and atlleast two pairs Eof contacts 'ducechosen remote control effect in said keying meanscouplingsaid.secondgener- '2. In a'remote control system transmittingapparatus comprising means for keying and modulating a carrier wave witha' train of recurrent signal elements each element of which ischaracterized as a predetermined control frequency, a "driven multiplexdistributor for transmitting said -signal -elements in repeatedsequences in pairs, receiving apparatus including amplifier,discriminator and detector stagesrand circuits for g g including amulti-channeldistributor in- 'said shifting the phase ofcertain lowfrequency comv V r g :ponents which are products of detection, andcscommutatmgmeans andcmtactsm saldvkeymg ating means to said-modulatorto provide 'fOIlthlE transmission of modulationpulses inpairsyseparate-controls for said keying means to separately or combindlytransmit one. pulse'pair forzii'ghtleft steeringcontrol upon a dirigiblebody'and one pulse pair for up-down elevator control upon said body. i.9. "The combination i a'ccor'ding to :claim 6 and ,dphasemompamtorcircuits for producing a com means for-feedingmodulationfrequencyenergies trol voltage the relative positive polarityof which selectively" t' chanhel components"6f depends upon hether thedetection products of commutating means, said channeltwo paired signalelements are combined in phase *components'theh fviictidfling a b gna sagreement or contraphasally 7 as desired 'for rem'ote control purposesand at 3, h bi ti according t 1m 2 d "least-oneof=saidchanne1 componentsof said comincluding means for interjecting into said trainmutatingmeans being selectable totransniit a "of signal elements othersignal elements rectifi- "sig lpiilse for camouflage Pu 'D S cationofwhich is to confuse an unauthorized 10. In a remote control systemffortas'teerin recipient of the signals. device responsive to carriercurrentsmodulated 13 in repeated sequence at a constant predetermined rate by atleast two currents of different frequencies wherein the time sequence ofthe modulating currents is altered for control purposes, a frequencydiscriminator and detector system 'excited by said modulated carriercurrents for deriving pulses of A.-C. the pulse frequency of whichcorresponds to said constant rate and the relative times of occurrenceof which change when said sequence is altered, and control apparatusresponsive to said pulses of A.-C. for controlling said steering device.

ELLISON S. PURINGTON.

REFERENCES CITED Number 14 UNITED STATES PATENTS Name Date Mirick -1Aug. 24,1926 Loftin June 24, 1930 Phinney Dec. 27, 1938 Luck Mar. 18,1941 Koch June 10, 1941 Tunick May 5, 1942 Boswau Aug. 3, 1943 GanahlJan. 29, 1946 DeBey Mar. 5, 1946 Kellogg Apr. 2, 1946 Moynihan Oct. 1,1946

